Nairobi, Kenya — Kenya’s four-month-long Great Wildebeest Migration began this month, with herds of animals crossing the crocodile-infested Mara River into the Maasai Mara Game Reserve from Tanzania's Serengeti park, and tourists have begun their own mad rush to the Kenyan bush to take in the spectacle. This was never just a matter of wildebeests on the move, because where the wildebeests go, leopards, lions, and hyenas inevitably follow.

But for mass migration, and for hungry lions, tourists need go no farther than Nairobi.

Over the past six months, stray lions from Nairobi National Park, on the capital city's outskirts, have been venturing into Nairobi's suburbs, preying on cattle, sheep, and goats. It's a matter of concern to members of the Masai community, who live off of herding on the outskirts of Nairobi, and who are demanding action from the government. Some Masai have already begun killing lions to protect their herds and families.

The human-wildlife conflict – an almost inevitable factor of life in Nairobi as human settlement moves ever closer to national parks and wildlife areas – peaked in June, when Masai warriors speared to death six lions in Ilkeek-Lemedung'i village in Kitengela area on the southern side of the park. The predators had killed 13 goats and sheep, and mauled one person in an attack, according to members of the community. Three other lions were killed in December 2011 and January 2012 near Nairobi Park. Although killing lions is illegal here and the Kenya Wildlife Service (KWS) has promised to arrest the killers, no one has been arrested or charged.

“The killings are regrettable, but this was a reaction of the community which feels frustrated and threatened. The situation has gone from bad to worse,” says Sidney Quntai, the chairman of Kenya Coalition for Wildlife Conservation and Management, a civil society organization. “It is difficult to sleep peacefully at night, since one has to keep ears and eyes open. In case of noise one creeps out to see if the animals are safe,” adds Mr. Quntai.

Located seven kilometers from Nairobi, and covering 44 miles square, Nairobi National Park is by no means the only park in the world located near a major metropolis. The Indian city of Mumbai, for instance, has Sanjay Gandhi National Park, home to leopards who occasionally prey on the animals of shack-dwellers who live on its perimeter. But Nairobi's claim of sheltering the “big five” – lions, leopards, elephants, buffaloes, and rhinos – does help to attract thousands of local and international tourists.

In a country where tourism makes up 12 percent of gross domestic product, and 21 percent of its foreign exchange earnings, nobody wants to do anything that might disrupt that business. But when lions prowl the suburbs of a capital city, the call for action is inevitable.

At the roots of Nairobi's lion problem are changes made to Kenya's land-tenure system, which has allowed owners of pastureland around Nairobi National Park to sell their land. Many of these new property owners erect fences, which blocks the migratory corridor of antelopes, wildebeest, and other animals who inhabit southern Kenya and northern Tanzania. In the past, many of these animals moved from national park to national park, but as fences have gone up, fewer herding animals can make the return journey. This leaves lions without food, so the lions begin to look for other options.

Among the lion's best options are the cattle, sheep, and goats herded by Masai tribesmen, who have migrated along that same southern-Kenyan corridor for centuries. So as the fences go up, blocking the migration of animals from Nairobi National Park to Tsavo and Amboseli National Parks farther south, it is the domestic herds of the Masai that become the lion's favorite prey.

“The land system in use is no longer compatible to the animal numbers," says Mr. Quntai. "Therefore animals in the park have moved to graze in the areas where the communities graze their livestock. The big cats have followed the herbivores. We have seen zebras going to graze with the livestock and sleeping out with the cattle near the Manyatta (traditional Masai homestead).”

According to Friends of Nairobi National Park, a nonprofit volunteer-driven organization, there were 29 adult lions in the park by June, with 11 cubs younger than 6 months old. From October 2011 to June 2012, the lions attacked 72 times, killing 23 cows, 138 sheep and goats, and 4 donkeys.

The lions are preying on livestock in areas where there are few shepherds to guard them, according to the organization. Lions are certainly capable of attacking and killing cattle, but they appear to have developed a liking for sheep and goats, sometimes walking past cows. Having lived in proximity to humans for their entire lives, they are no longer frightened by humans or lights. Some jump over backyard walls or break through chain-link fences in pursuit of livestock, the organization says.

With people sharpening their spears and richer citizens loading their rifles, the KWS has been appealing for calm. KWS spokesmen stress that the solution to this conflict can only come through changing the land-management and wildlife-conservation policies of the country.

For the short term, he says, KWS has established rapid-response teams, built electric fencing, and begun teaching courses in conservation awareness. Kenya’s current laws do not provide for compensation to farmers who lose stock, Mr. Udoto says, but a new proposed law has a provision for the compensation.

Quntai says the Masai community is skeptical. Masai people want the country's Wildlife Act to be rewritten to protect people, to provide compensation for human lives and livestock lost, and to share some of the tourist dollars generated through the national parks.

“If they don’t enact the law, the wildlife will disappear,” said Mr. Quntai.

KWS says Kenya’s lion population has dropped to 2000 in 2012 from an estimated 2,700 in 2002. The greater Nairobi ecosystem has 46 of them.